With current trends toward longer life expectancy the occurrence of atrial fibrillation increases significantly in all industrial nations. Currently atrial fibrillation is the main cause for hospitalization in the U.S.A. for arrhythmic disorders. It is also the most underlying reason for cerebrovascular stroke events. A solution to atrial fibrillation diseases are favored to correct its complication upon life and increase life expectancy, and also hemodynamics and thromboembolic complications favor a solution to such diseases by converting atrial fibrillation into sinus rhythm. However the use of antiarrhythmic drugs effective to preserve sinus rhythm produce a significant risk of proarrhythmias and reduced survival rate.
Also external shock with energies between 100 and 350 joules is a standard therapy for converting atrial fibrillation into sinus rhythm. The risks and complications of this type of therapy include late ventricular fibrillation, pericarditis due to the high electrical current and fractures of the spine and ribs following muscular contractions with high energy shock application.
The art of implanted atrial defibrillation electrodes using lower energies is well developed, as disclosed for example by J. Adams, et al. in U.S. Pat. No. 5,282,837, Feb. 1, 1994 for Atrial Defibrillator and Method. Therein, defibrillating energy is released from an implanted defibrillator for discharge between two electrodes of an implanted catheter threaded through the coronary sinus with energy discharge electrodes respectively located in positions beneath the left atrium near the left ventricle and in a region adjacent the right atrium coronary sinus ostium for minimizing ventricular fibrillation potential. The implanted defibrillator senses arrythmia and controls the energy discharge.
Ventricular fibrillation is also arrested with implanted systems as disclosed by T. Shulte, et al. in U.S. Pat. No. 5,269,319 by means of two defibrillation electrodes on a single catheter inserted via the superior vena cava into the right atrium and right ventricular cavity respectively. This system discloses the manner in which the defibrillation impulse energy is synchronized with the R-waves and provides for detection of the R-waves for that purpose.
It is a general object of this invention to provide improved treatment of atrial fibrillation on a temporary basis and correct the foregoing deficiencies of the prior art.
A further objective of this invention is to significantly reduce the amount of energy required for treatment of atrial fibrillation from external impulse generators with a hybrid system of internal defibrillating electrodes powered by external energy and control means.
However there are problems related to prior art electrodes both in the necessity to implant and the requirement to process enough energy for defibrillation in circumstances. In particular the effort that it takes to install and operate implanted systems is not tolerable when life atrial fibrillation occurs only rarely. The nature of effective prior art electrodes is generally intrusive with large electrode areas necessary to handle the high energy impulses that can initiate rejection reactions in the human body. Also implantation of netting, barbs and anchors in the region of the heart is not tolerable and not feasible for only temporary systems.
There are such conditions as congestive heart failure which after defibrillation can require continuous monitoring rather than isolated shock treatment. Furthermore cardiac surgical conditions that need post-operative monitoring for atrial dysrhythmias and defibrillation, require instantaneous treatment when atrial fibrillation is detected.
Accordingly it is a further object of this invention to provide a method and accompanying instrumentation for temporary use for limited periods of time to continuously monitor and instantaneously to treat dysrhythmias and atrial fibrillation with adequate electric field gradient shock energy, without implantation.
Other objects, features and advantages of the invention will be found throughout the following description, the accompanying drawings and the claims.